Teaching grandmother to suck eggs

Teaching grandmother to suck eggs is an English language saying meaning that a person is giving advice to someone else about a subject about which they already know (and probably more than the first person).[1] "Egg sucking" removed the egg contents while preserving the shell intact. Two small holes were made on the ends of the egg, and the contents sucked out. The shell could then be painted or otherwise used for decorative purposes without it becoming rotten and smelling bad.

“I remember my old schoolmaster, who was a prodigious great scholar, used often to say, Polly matete cry town is my daskalon. The English of which, he told us, was, That a child may sometimes teach his grandmother to suck eggs”

"You see, Grandmama, before you extract the contents of this bird's egg by suction, you must make an incision at one extremity, and a corresponding orifice at the other." Grandmama's response is to the effect, "Dearie me! And we used to just make a hole at each end."

"To teach one's grandmother to suck eggs – To offer needless assistance; to waste one's efforts upon futile matters; especially, to offer advice to an expert. This particular expression is well over two hundred years old; it is just a variation of an older theme that was absurd enough to appeal to the popular fancy.

"The purpose of this exercise is to follow precise unnecessary directions issued by a higher HQ. You have been directed to be in possession of a fresh empty eggshell for no apparent reason. Simple issuance of tasks being insufficient in any anal-retentive, career-oriented, hopelessly bureaucratic military staff society, the staff of the higher HQ have issued the following instructions."

Sméagol instructed his grandmother, as related in the Riddle Contest in Chapter Five of The Hobbit:

"But suddenly Gollum remembered thieving from nests long ago, and sitting under the river bank teaching his grandmother, teaching his grandmother to suck — ‘Eggses!’ he hissed."